The present invention relates generally to electrostatic discharge protection devices. More particularly, the invention relates to electrostatic discharge protection devices for semiconductor chip packages CSCP") where the electrostatic discharge protection device connects selected pins on the SCP so they are grounded or maintained at the same electrical potential to inhibit electrostatic charge accumulation when the SCP is not mounted on a circuit board, and disconnects the ground connection upon operative combination of the SCP on the circuit board or, optionally, disconnects the ground connection manually by a user.
Electrostatic charge is a stationary electric charge which accumulates on various surfaces. An electrostatic discharge occurs when the electrostatic charge becomes substantial enough to overcome a dielectric material between the charge and another surface of lower electrical potential. An example of such a discharge as naturally occurring is lightning.
Electrostatic discharge in the realm of electronics can be devastating to microelectronic devices. A sharp voltage spike caused by an electrostatic discharge can cause permanent and costly damage to individual precision devices, such as random access memory or other semiconductor devices, inter alia.
Many commercially available electrostatic discharge protection devices in use today consist primarily of electrostatic discharge packaging of the SCP in electrically conductive strips, pellets, boxes, and plastic tubing which provide effective electrostatic discharge protection until the user is about to insert the SCP into complementary receptacles on the circuit board. At that point the user must remove the electrostatic discharge packaging from the SCP thus rendering the SCP vulnerable to electrostatic discharge in order to position and insert the connector pins into the receptacle. Accordingly, as the user inserts the connector pins of the SCP into the receptacles, the semiconductor dies housed within the SCPs could be destroyed by electrostatic discharge and the SCP would therefore have to be replaced. Moreover, certain types of SCPs, typically EPROMs, UVPROMs, and DRAMs are plug-in devices which have connector pins which are repeatedly inserted into and then removed from the receptacles. These types of SCPs require electrostatic discharge protection during the repeated insertions into and removal from the receptacles. Specifically, the connector pins of those SCPs require electrostatic discharge protection from the moment that their connector pins are removed from their receptacles until their connector pins are again inserted therein.
In some instances, where the receptacle itself is later subject to Electrostatic Discharge, it is advantageous to allow the electrostatic discharge protection device to remain in place and be switched manually to a de-shunted position.
Consequently a need still exists within; the semiconductor chip packaging industry for a true electrostatic discharge protection device, rather than electrostatic discharge protection packaging which effectively protects the semiconductor die from electrostatic discharge until the connector pins of the SCP are inserted into the receptacles of the connector and then protects the semiconductor die from electrostatic discharge again when the connector pins are removed from the receptacles. Surface mount microelectronic devices have an additional problem in that they often have numerous small pins, often on all four sides of the SCP, thereby making the surface mount device difficult to handle. A prior art electrical connector receptacle arrangement is described in commonly assigned U.S. Pat. No. 5,108,299 entitled "Electrostatic Discharge Protection Devices for Semiconductor Chip Packages" by David V. Cronin issued Apr. 28, 1992. This patent shows a shunt attachment placed on pins of the semiconductor chip package arranged to provide a short circuit across selected pins. Upon insertion into the receptor, the attachment is driven away from the semiconductor chip package, causing the short circuit to be broken. While this arrangement is an improvement and is useful for connectors for semiconductor chip packages such as DIPs, Dual Inline Package, the design requires that they be fairly large and clip to the semiconductor chip package which in the case of surface mount or other chips having pins on all four sides or numerous small pins, this can become unwieldy.
Other commonly assigned patents and copending applications include U.S. Pat. No. 4,971,568 entitled "Electrical Connector With Attachment For Automatically Shorting Select Conductors Upon Disconnection of Connector" by David V. Cronin issued Nov. 20, 1990, U.S. Pat. No. 5,163,850 entitled Electrostatic Discharge Protection Devices For Semiconductor Chip Packages" by David V. Cronin issued Nov. 17, 1992, U.S. Pat. No. 5,164,880 entitled "Electrostatic Discharge Protection Device for a Printed Circuit Board" by David V. Cronin issued Nov. 17, 1992, and pending U.S. application Ser. No. 234,917 entitled "Electrostatic Discharge Protection Device" by David V. Cronin filed Apr. 28, 1994.
In the case of surface mount microelectronic devices, or other SCPs which have large quantities of connector pins, additional problems arise in the difficulty of manufacturing the prior art electrostatic discharge protection devices and a loss of rigidity of the electrostatic discharge protection devices over a long span. With respect to the latter, if the electrostatic discharge protection device has only two points of contact for a row of connecting arms, one on each end, a long span causes the middle of the row to lag the outer parts of the row when pulling away due to flex in the structure over the long span.
Accordingly, it is an object of this invention to provide electrostatic discharge protection devices which operate to automatically open a short between selected conductors upon connection with a mating receptacle or are adapted to manually open the short circuit if a user desires the electrostatic discharge protection device to provide additional protection, such as electrical shielding while in place.
It is another object of this invention to provide electrostatic discharge protection devices for use with SCPs having numerous small pin conductors without sacrificing rigidity along the length of the structure.
It is still another object of the invention to provide an electrostatic discharge protection device which is easier and, therefore, less costly to manufacture.
These and other objects of the invention will be obvious and will appear hereinafter.